The present invention relates generally to fired ceramic wares and is more particularly concerned with the preparation of fired ceramic wares exhibiting hydrophobic characteristics throughout the bodies thereof.
It is often desirable to provide ceramic wares with hydrophobic characteristics. Conventionally, ceramic wares are waterproofed or rendered water-repellent by vitreous glazing or by coating or impregnation thereof with diverse water-repellent liquids such as water, glass, waxes, greases, hydrocarbon oils or organosilicone fluids. In the case of vitreous glazing the surface of the ware is provided with a continuous glassy surface coating, said coating serving to prevent the passage of water therethrough into the body of the ware. However, since glazing is only a surface treatment, the body of a glazed ceramic ware is itself not rendered hydrophobic. Therefore, should the continuity of the protective glaze be imperfect, or broken, the body of the ceramic ware can then absorb water through such glaze defect. Moreover, glazing does not ordinarily provide surface water-repellency of such degree that water will quickly bead up and flow readily from a glazed surface. Rather, it is more common that glazed ceramic wares, particularly upon weathering thereof, are sufficiently wettable as to allow the formation of water films thereover. This represents a particularly acute problem as regards glazed ceramic high voltage insulators commonly employed in conjunction with power lines. The surface dielectric properties of such insulators can often degrade substantially upon exposure to rain, fog, snow, ice or condensation and the resulting power losses associated with such degradation can be considerable.
There are commercially available waterproofing compositions which can be applied to structural ceramics such as bricks and tiles. Unfortunately, such coatings are usually only temporarily effective, do not confer hydrophobicity throughout the entire body of the ware and are difficult to apply uniformly. Moreover, the use of such coatings can often diminish the permeability of the ceramic ware treated therewith, which permeability is often a desirable characteristic.
In outdoor applications, upon breakdown of a waterproof coating or glaze, water usually enters into the body of a ceramic ware and can cause severe physical degradation thereof, particularly when the ware is subjected to freeze-thaw cycling. In accordance with the present invention, however, there is provided a method for the preparation of novel fired ceramic wares possessing exceptional surface water-repellency and hydrophobic properties throughout the ceramic bodies thereof.